maybe you even know a pair of very smart twins. but erika has a story about quadruplets -- four siblings, each one of them qualified to join a club of intellectual superstars. >> they don't look exactly alike, but these teens have a very special bond -- they're quadruplets, very accomplished quadruplets. for example... >> [ speaking mandarin ] >> ...patrick, thomas, and alanna learned to speak mandarin chinese. >> sister moria focused on learning sign language instead. what makes this unusual is that they started learning these languages before they were even in kindergarten. >> i was told that most kids entering kindergarten couldn't write everybody's name in the house, couldn't tie their shoes, couldn't read, and didn't have an understanding of two other languages. and i didn't know that. i thought that they had to have these skills to go into kindergarten. >> by the time they reached high school, the crowley quads had a high profile in their hometown of wylie, texas. >> sit! >> in addition to service projects like training guide